function MVTLayer(pbf, end) {
	// Public
	this.version = 1;
	this.name = null;
	this.extent = 4096;
	this.length = 0;

	// Private
	this._pbf = pbf;
	this._keys = [];
	this._values = [];
	this._features = [];

	pbf.readFields(readLayer, this, end);

	this.length = this._features.length;
}

function readLayer(tag, layer, pbf) {
	if (tag === 15) layer.version = pbf.readVarint();
	else if (tag === 1) layer.name = pbf.readString();
	else if (tag === 5) layer.extent = pbf.readVarint();
	else if (tag === 2) layer._features.push(pbf.pos);
	else if (tag === 3) layer._keys.push(pbf.readString());
	else if (tag === 4) layer._values.push(readValueMessage(pbf));
}

function readValueMessage(pbf) {
	var value = null,
		end = pbf.readVarint() + pbf.pos;

	while (pbf.pos < end) {
		var tag = pbf.readVarint() >> 3;

		value = tag === 1 ? pbf.readString() :
			tag === 2 ? pbf.readFloat() :
				tag === 3 ? pbf.readDouble() :
					tag === 4 ? pbf.readVarint64() :
						tag === 5 ? pbf.readVarint() :
							tag === 6 ? pbf.readSVarint() :
								tag === 7 ? pbf.readBoolean() : null;
	}

	return value;
}

// return feature `i` from this layer as a `MVTFeature`
MVTLayer.prototype.feature = function(i) {
	if (i < 0 || i >= this._features.length) throw new Error('feature index out of bounds');

	this._pbf.pos = this._features[i];

	var end = this._pbf.readVarint() + this._pbf.pos;
	return new MVTFeature(this._pbf, end, this.extent, this._keys, this._values);
};